Uninstalling Plug-ins

I read somewhere once, that the best way to screw up your blog is to install a bunch of plug-ins while testing them out, even if you delete them later.

What I would like to know is, if I install plug-ins to try them out and then delete them, am I leaving behind a trail of clutter that could negatively impact my site’s performance?

If so, what I can I do to completely get rid of the trail?

Thanks!